Could the change of the LCD lamp lead to dark spots on LCD?

[wisdomkeeper]

My friend gave me ThinkPad T40, because when he tries to switch it on, the image on the screens seems to be with red nuance and after not more than a second the back light shuts off. I immediately thought that this is issue with the CCFL LCD lamp. I've replaced the CCFL and the backlight is back. The lamp with which I replaced the faulty one was OK, I did some testing before assembling everything. But after assembly I found that there are darker areas/spots on the LCD, down left and down right. The rest of the screen is perfectly normal, so I don't think that this is a misplaced lamp.
But could the replacement of the LCD lamp lead to this? Honestly, I did not looked carefully on the screen when the Thinkpad came to me. I don't know if this is old problem, because of the liquid spilled on the screen or etc. But this question doesn't give me the peace. If this is my fault, how could I fix this and why this happened? In the past I have replaced the CCFL-s of multiple LCD panels and everything was OK, until now...

[systemBuilder]

You have learned for yourself why most people don't bother replacing a CCFL lamp on an old TFT display,they just spend $80 for a new one :

(a) The glass and/or plastic diffuser of an old display turns yellow, so a re-lit display is not "pure white" like a newly-made display.
(b) Pressure spots eventually will ruin every display. A pressure spot is a place on the screen where somebody has applied excessive pressure.

In my current laptop (a swap from my employer), there is a pressure spot on the lower left edge of the display. The spots tend to happen on the edge of a display because that's about as far as one can reach when pinching the display. For example, if you pinch the display to pick up or move the laptop, you will almost certainly damage the screen and produce a pressure spot. There is not way to repair to this problem, sorry.

If the dark spots are completely and totally even, then perhaps your CCFL lamp was a few millimeters too narrow and so it's not lighting the edges well. If you look at some of the reviews on www.notebookcheck.com, two thirds of the way down they always divide the screen into 9 divisions and measure brightness, and most screens are highly non-uniform, even today :

http://www.notebookcheck.net/Review-Upd ... 966.0.html

For example, the new Thinkpad e545 screen varies from 205 candles (lower left) to 252 candles (very middle) in brightness.

- Don

[wisdomkeeper]

Thanks. Personally, I think that the dark spots in this case are produced by excessive heat, produced of the dying CCFL lamp. Usually, when they CCFL is near of the end of it's life, it tend to release excessive amounts of heat.
p.s The whole laptop doesn't worth 80$. Buying a new screen isn't economically justified

[topshot]

Just like any fluorescent tube lamp, the ends are always a little darker.

I put in the recommended bulb for a nice t42p UXGA and the corners are a little darker than everything else. The CCFLs also have small metal ends which limits the output there as well.

[RealBlackStuff]

Screens that have bad spots already, do not always show these up with a weak/dying CCFL.
They only become visible when a new tube is put in.
A new tube normally displays evenly all along its length.

[systemBuilder]

DISCLAIMER : I have not tried this during a backlight replacement.

There is one thing you can do to fix an old, yellowed, thinkpad diffuser, to turn it white again. Wipe it down (EVENLY) with acetone. Acetone will dissolve most plastics, taking the old, yellowed outer layer of plastic off the diffuser, and turning it white again. I have a great deal of experience in using acetone to restore rubber and plastic ancient bicycle parts. It works pretty quickly (just 3-4 wipes at most), and it's possible to get an uneven finish if you concentrate too much in one area. I am going to try it with my most yellowed display, as soon as I can find all the thinkpad parts (including backlight) that were lost in our recent house-move.

DISCLAIMER : I have not tried this during a backlight replacement.

[Neil]

^^ Would be interesting to see if it works on a diffuser, but I don't plan on trying it out. Just no longer interested in trying to repair LCD panels...too much trouble IMHO.

[RealBlackStuff]

@systemBuilder:
Acetone on plastic? NEVER EVER!
You tried to push this idea before, and got properly ridiculed for it.
I suggest you stick to your bicycles and leave laptops be...

[Cigarguy]

WOW! Acetone on something this delicate? Let's ignore chemistry and assume it works. Can you possibly do this without scratching the screen? I know I can't.